Oxytocin: a paracrine regulator of prostatic function.

It is now well established that the peptide oxytocin can act as a paracrine factor as well as a classic hormone. Oxytocin is produced locally in both the testis and ovary, where it may modulate both steroidogenesis and contractility of the male and female reproductive tracts. The peptide is also present in the prostate and seminal fluid and there is growing evidence that oxytocin may be produced in the prostate. Within the prostate, oxytocin has been shown to increase growth of the epithelial tissue and increase both muscular tone and contractile activity. Furthermore, prostatic concentrations of the peptide are regulated by androgens. It is hypothesized that oxytocin may act as a paracrine factor to regulate cell growth and that this may be secondary to its effects on the enzyme 5 alpha-reductase which converts testosterone to dihydrotestosterone. In addition, oxytocin may be involved in the pathophysiology of benign prostatic hyperplasia.